How to find out which devices use the most power in your home

Although the UK Government has capped the price of power, our bills are still set to rise again in October. If you want to cut costs, you need to know where your power is going. Once you know that, you can change your habits and save money.

We’ll explain to to find out how much electricity different devices and appliances use, so you can decide how often or how best to use them. For example, you might find out that the dishwasher setting you normally use is not the most energy-efficient one.

There are two ways to find out how much power a device or appliance is using. The first, best and easiest way is to use a power meter. This will give you very accurate information and allow you to compare different cycles on your washing machine and dishwasher, or different settings on a heater or air purifier to see which are the most power-hungry.

The second way, which is useful for simpler plug-in items like a kettle, is to use the appliance’s wattage and information from your electricity bill or an online calculator to see how much power it uses in an hour.

In this article, we’ll show you how to do both.

How to use a power meter to find out how much electricity a device uses

First, buy a power meter. They cost from $15 (try this one on Amazon) / £15 (this one from ebay) and will give you more information than simply how many watts a device is drawing at any given moment, though this is still very useful to know.

It may seem counterintuitive to spend money on a power meter, but it could pay for itself many times over once you’ve identified how to use your appliances economically.

To use a power meter, unplug the appliance you want to measure, and plug power meter into the mains socket. Then plug the appliance into the power meter.

If there isn’t enough room, or you cannot see the display because the socket is awkwardly located, then use a mains extension cable and plug the power meter and appliance into that.

Turn on your appliance and the power meter should show how many watts are being used. You can use this to see if the appliance uses as much as the user manual claims: it might be a little higher or lower because the figure quoted is usually an average, or a maximum.

Here’s how to measure how much power a dishwasher or washing machine cycle costs

1. Plug your appliance into the power meter, which itself should already be plugged into a mains socket
2. Turn on your appliance and set it to the programme you want to check – this could be the fastest mode, standard cycle or eco mode
3. Set the power meter’s display to show kWh (or cost) rather than watts. Use its manual if it’s not obvious how to do this.
4. You can usually enter the unit rate – the cost per kWh (kilowatt-hours – the that your supplier charges – to see the actual electricity cost.
5. Run the programme.
6. When it finishes, you’ll see how many kWh were used and, if you set the unit rate, how much that has cost.

In the example below, my dishwasher’s standard cycle used 0.7kWh at a cost of 22p, because my supplier charges 31p per kWh.

If your power meter does not support cost, you can calculate the cost by multiplying the number of kWh used by the cost per kWh. In the example here, the calculation would be:

• 0.713 (almost 3/4 of a kilowatt hour) x 31 (pence per kilowatt hour) = 22.1p

Power meters often have other functions, such as the average wattage over time (useful for things like TVs and printers), as well as the maximum and minimum wattage used.

Of course, the other obvious thing you can use a power meter for is to check how much a device uses in its standby or ‘off’ mode. Modern devices – usually by law – should consume no more than 0.5W when off.

If you find one that uses more, you can switch it off at the mains socket to prevent it costing you money unnecessarily.

Some people go around switching sockets off at bed time or even after they finish using an appliance. That, however, is barely worth the effort in terms of cost saving unless you have dozens upon dozens of appliances all using 0.5W.

Even at the new higher rate (see below), 20 devices running in standby for an entire year would cost you roughly £25. The biggest savings will come from other changes, including using eco modes and making sure you only wash full loads.

How to use your electricity bill to find out how much electricity a device uses

1. Electricity standing charge

If you have a look at one of your power bills, you will see that your electricity charges are broken down into two parts: the electricity standing charge and the electricity unit rate.

The electricity standing charge is the amount you pay each day for your electricity service, regardless of how much electricity you use. According to the Energy Savings Trust, the average standing charge in England, Scotland and Wales based on the April 2022 energy price cap is 28p per day for electricity on a standard tariff, which comes to £165.48 per year. However, these numbers are due to rise again in October, in line with the recently announced energy price cap.  

For reference, here are the new maximum standing charges and unit rates that energy companies are allowed to charge from 1 October 2022:

• Electricity unit rate: 34p per kWh
• Electricity standing charge: 46.4p per day

• Gas unit rate: 10.3p per kWh
• Electricity standing charge: 28.5p per day

Unfortunately, it’s not easy to measure how much gas individual appliances use (such as a gas hob, gas fire or boiler). Plus, we’re focusing on electricity use here, not gas.

There are a few UK suppliers which do not charge their customers a daily fee, so you can look for a supplier that offers this. However, you will also need to compare electricity unit rates (read on to find out what these are), so you can’t escape doing the rest of the calculations. A switch based only on the standing charge could end up costing you more.

People who travel frequently – who are away for more than half of the time – should look into a no standing charge tariff right away. Be wary of using comparison sites to calculate whether or not this would be cheaper for you. These sites will usually ask you for your monthly usage – but if you’re away a lot, that in itself will vary hugely.

2. Electricity unit rate

Your electricity unit rate is the second part of your electricity charge. It is calculated in cost per kilowatt hour (kWh). This is a standard unit of measurement that would keep a 1,000 watt appliance running for one hour.

According to the Energy Savings Trust, based on the April price cap, the average standard rate electricity charge is 28.3p per kWh in England, Scotland and Wales. Bear in mind that it’ll vary depending on where you are, and that it is set to rise again.

In the United States, according to the Environmental Investigation Agency, the average price a residential customer paid for electricity in June 2022 was 15.42 cents per kWh – but this figure varies hugely from state to state.

Calculating the cost of running an appliance

Once you know your kWh charge, you can start to break down your electricity bill by appliance. To calculate what each device costs to run, choose an appliance and have a look at its wattage label. Multiply the wattage by the number of hours you use it and divide the result by 1,000. 

A very simple example is this: if you pay 23p per kWh and your microwave is 1,000 watt, it will cost you 23p to run it for an hour. Of course, it’s not very likely you’ll use your microwave for an entire hour. But imagine that you run it for at least an hour every week. That means that over the course of the year, your microwave is responsible for about £11.96 of your electricity charges.

GoCompare has some useful examples of what 1 kWh can do:

• Boil a kettle 10 times
• Do the ironing for an hour
• Run a fridge-freezer for three hours
• Watch seven hours of television

Using an online energy calculator

If you don’t have an energy bill, or find it complicated to calculate, you can use this Sust-It calculator. It’s up-to-date, with figures based on the October 2022 price cap numbers. Just dd the wattage of the appliance you want to measure and how long you use it for and it’ll give you the running cost.

Here are some rough findings for common devices and appliances. I’m using a 34p tariff – which is in line with the October price cap – for the calculations.

• If you had a 52” LCD TV and you left it on for 24 hours, it would cost you about £2.28 in electricity. If you regularly fall asleep in front of your TV, by the end of the year these could be expensive naps.

• A fan heater is one of the most expensive small appliances to run. Use it sparingly. If you left it on for 24 hours, it would cost you £14.69.

• A kettle costs you a pricey 51p per hour of use. Keep it descaled and don’t put in more water than you’ll use each time to make it as energy efficient as possible.

For more energy saving advice and information, find out if smart heating could save you money and have a look at our round-up of the best smart thermostats we’ve tested.